cylinder(s). If your issue is injector related, this will help you focus on the troublesome area. There have been lots of posts lately about CAS and PTU issues, so I'd focus on them as well. How's your wiring? No ECU codes I'm guessing? How are your O2 sensors? Engine and Fuel Temp Sensors? AAC/FICD also have idle implications, and don't forget to properly adjust your TPS :) Just a few things.....